1. Field of the Invention
This invention relates to a solenoid valve and more particularly to a solenoid valve for controlling an actuator by switching over the supply of pressure thereto.
2. Statement of Prior Art
One conventional type solenoid valve is shown in a Japanese utility model application laid open on Aug. 19, 1975 as JitsuKai sho-50-100132. The necessary amount of the electro-magnetic force for moving the valve is provided by a solenoid coil. Accordingly, when the fluid flow is very large, the amount of the electro-magnetic force must be larger for moving the valve. This requires that the solenoid coil be made larger to overcome the fluid pressure at the valve. However, when the valve is in its closed position, a large force is needed for holding the valve closed. In addition, it is necessary to provide a large effective sealing area when a large amount of fluid flows therethrough. Thus, it is also necessary to provide a larger solenoid coil for overcoming the pressure difference generated at the valve.